The present invention relates to an auxiliary power source, and more particularly to a battery life monitoring system which assures the availability of a backup battery without continued monitoring of the backup battery.
Many vehicles include a data logging system which monitors and records a multiple of vehicle systems and events. The system typically monitors and records such vehicle parameters as engine performance, brake system usage, transmission shift points and other vehicle information. Importantly, the data logging system typically includes a real time clock (RTC) which allows the data logging system to record the occurrence time and duration of each vehicle event.
The system commonly draws power from an external power source such as a main vehicle battery. In some instances, such as during vehicle maintenance or main battery failure, the system could be without power. Loss of system power would alter the RTC and possible result in data loss. An auxiliary power source such as a battery backup is typically integrated with the system to assure that a power source independent of the external power source is always available to the system.
Over time and usage even the auxiliary power source will become unable to power the system should the external power source be unavailable. As this is undesirable, an auxiliary power source monitoring system is typically provided for the data logging system. To monitor the auxiliary power source at all times, however, would drain power from the auxiliary power source and thereby reduce the auxiliary power source""s life.
Accordingly, it is desirable to provide a monitoring system for the auxiliary power source which does not draw power from the auxiliary power source.
The system according to the present invention generally includes a data logging unit, a primary power source, an auxiliary power source and a controller.
The data logging unit monitors and records vehicle event data from each of a plurality of vehicle components. The data logging unit preferably stores vehicle event data from each component in a memory for later analysis and diagnosis. The data logging unit further records time data associated with the vehicle event data through a clock.
During normal system operation, the primary power source provides all necessary power. Should, however, the primary power source becomes unavailable, the system draws from the auxiliary power source to prevent data loss. The controller detects whether the primary power source is available or unavailable and the time at which it became available or unavailable. From the time data the controller will then determine the total time the primary power source was unavailable to power the system. This is the auxiliary power source usage time period. In other words, this is the duration of time that was drained from the auxiliary power source during which the primary power source was unavailable.
The controller reduces a predetermined auxiliary power source value by the auxiliary power source usage time period. The predetermined auxiliary power source value is a calculated value based upon the expected life of the auxiliary power source and is typically available from the power source manufacturer. Upon each occurrence in which the primary power source again becomes unavailable, the controller performs the same operations and further reduces the previously reduced predetermined auxiliary power source value by the next auxiliary power source usage time period. Reduction in the predetermined auxiliary power source value will continue until a predetermined value is reached.
The controller identifies when the predetermined auxiliary power source value reaches the predetermined value and triggers an alert. The alert is preferably a warning light or the like which indicates to an operator that the system requires service. During service the auxiliary power source is replaced and the predetermined auxiliary power source value is reset.
The present invention therefore assures that an auxiliary power source is always available without actually requiring a sensor connected to the power source.